The rapid development of long term evolution (LTE) network opens up new opportunities to both mobile carriers and device original equipment manufacturers (OEMs). Due to higher throughput, lower latency and faster connection times, many new applications related to the LTE network have emerged. For example, voice over LTE (VoLTE) technique which transmits higher quality voice calls through an LTE network provides the salient advantages such as higher efficiency and robust global roaming. As the LTE networks are being continually deployed, the capability of mobile devices to perform seamlessly handover of VoLTE calls to non-LTE networks (e.g., circuit switched (CS) networks or WiFi network) will be a key technology for higher quality voice call experience to mobile users. Therefore, an efficient and seamless handover technique between the LTE and non-LTE networks is needed to improve VoLTE call performances and throughput.